Question 737182
{{{(sqrt(5) - sqrt(10)) / (sqrt(5) + sqrt(10))}}}
multiply top and bottom by {{{(sqrt(5) - sqrt(10))}}}
{{{(sqrt(5) - sqrt(10)) / (sqrt(5) + sqrt(10))*(sqrt(5) - sqrt(10)) /(sqrt(5) - sqrt(10)))}}}
factor denominator to difference of two squares
{{{(sqrt(5) - sqrt(10))^2/(5-10)}}}
{{{(5-2sqrt(15))/-5}}}